This chapter concerns the analysis of spatial patterns of points that lie on a network of lines, such as the pattern of road traffic accidents on a road network.

Figure 17.1 is a record of crimes in the period 25 April to 8 May 2002, in an area of Chicago (Illinois, USA) close to the University of Chicago. The original crime map was published in the university newspaper, Chicago Weekly News, in 2002. The graphic was scanned by staff of the Department of Statistics, University of Chicago, and manually digitised by Adrian Baddeley using clickppp and clickjoin (explained below).